Hydraulic steering mechanism



Aug. 3, 1954 1. A. L AUCK HYDRAULIC STEERING MECHANISM Filed Dec. 15, 1951 @i mw! w Patented Aug. 3, 1954 UNITED STAT TNT oFFICE HYDRAULC STEERING MECHANISM John A. Lauck, Shaker Heights, Ohio, assignor to Borg-Warner Corporation, Chicago, Ill., a corporation of Illinois 6 Claims. 1

This invention relates to power steering mechanism for steering the dirigible wheels of a vehicle. More particularly, the invention relates to .a simplified and improved fluid pressure boosted steering mechanism which can be easily installed `in a, vehicle embodying conventional mechanical steering.

Most power or power boost steering mechanisms which are produced today require the provision of a different gear box at the end of the steering column from that utilized in conventional steering arrangements. In addition, such mechanisms of the prior art ordinarily reduire some modiiications to the steering column plus the addition of complicated valving means and power steering linkages. As a result, most power steering devices of the prior art are expensive and difficult to incorporate in a vehicle. Consequently, there is a great demand in the highly competitive automotive field for an inexpensive power steering device which is durable and reliable and which can be incorporated in conventional mechanical steering arrangements with a minimum of change.

The steering mechanism of the present invention is intended to meet the demand for an il-- proved and simplified power steering device which can be easily installed in vehicles embodying conventional mechanical steering arrangements. The mechanism of the present invention can be installed by separating a conventional steering shaft into two parts and providing a simplied coupling therebetween. The coupling includes improved valving means for controlling the admission of pressurized iiuid to two sides of a reciprocable iuid piston which is connected to the pitman arm of the conventional steering device. The arrangement provides for graduated steering force to be applied to the dirigible wheels in response to the manual effort imposed on the vehicle steering wheel. The resultant mechanism `provides power boosted steering while still incorporating the required amount of feeL and in addition, conventional mechanical steering is provided for in the event of failure of the power boost means.

It is, therefore, an object of the present invention to provide improved and simplified mechanism for power steering of the dirigible wheels of a vehicle.

Another object of the invention is to provi-:le an improved differential fluid pressure type of "power steering device which functions on tordu-e "reaction and still has fail safe characteristics.

A `further object of the invention is to provide a power steering mechanism having improved control characteristics andk providing for substantially conventional mechanical steering characteristics in the event of failure of the power mechanism.

An additional object of the invention is to provide a differential fluid pressure type of power steering mechanism including improved and simplined valving means incorporated in a coupling for connecting the two portions oi a split steering shaft.

VStill another object of the present invention is to provide a simple power steering mechanism which can be easily installed in a conventional mechanical steering arrangement by forming `the steering shaft in two portions and providing a vsirrmlhed coupling therebetween and by including means for providing fluid under a pressure other than atmospheric .and a pressure actuated fluid motor.

A specific object of the invention is to provide a hydraulic steering mechanism which incorporates a simplified mechanical coupling between two portions of a steering shaft with the coupling including control valving means which incorporate feel into the mechanism and provide for power-boosted steering lefort in proportion kto the manual steering effort applied, said mechanism having fail safe characteristics.

@ther objects, features and advantages of the present invention will be apparent from the following detailed description cf one embodiment, by way of preferred example only, taken in conjunction with the accompanying drawings, in which:

Fig. l is a fragmentary, schematic view of la vehicle steering mechanism including power boost means according to the present invention;

Fig. 2 is an enlarged, schematic View, partly in section, of the coupling between the two portions of the steering shaft including the control valves and showing the connection with the fluid boost motor; and

Fig. 3 is a sectional View taken substantially .along line 3 3 of Fig. 2.

In Fig. 1 is illustrated mechanism for steering the dirigible wheels of a vehicle (not shown) and .including a steering wheel iii, a steering column H, and an upper, manually rotatable, steering shaft l2 to which the steering wheel is secured. The mechanism also includes a lower. rotatable, steering shaft lli, axially aligned with the shaft l2, a coupling l between the shafts, a steering gear box I6 at the lower end of the shaft Illl for translating rotary motion of the shaft M- into pivotal movement of a pitrnan arm il, a fluid reservoir I8, a fluid pump I9 and a fluid servo-motor or power boost cylinder 2e. The outer end portion or" the pitrnan arm Il is pivotally secured to a drag link 2| or the like, which connects with a steering linkage arrangement (not shown) for steering the dirigible wheels (not shown) of the vehicle.

In the operation of the mechanism of this arrangement manual steering effort, which is applied to the shaft I2 through the steering wheel lil, is multiplied by means of the boost cylinder 28 through pressure supplied by the pump I9, which is controlled by control mechanism included in the coupling l5 to be described.

The steering gear box I6 may be of any suitable design wherein rotary motion of the lower shaft Iii is translated into pivotal movement ci a steering box stub shaft 22 which is keyed or otherwise iixedly secured to the inner end of the pitman arm Il for imparting oscillatory movement of the drag link 2 I.

The boost cylinder includes a piston 23 which may be pivotally secured at 24 to the pitman arm Il' for pivoting the same about the axis of the stub shaft 22 in response to differential pressure applied to the piston through fluid conduits 25 and 2E communicating, respectively, with the opposite sides of the piston. The fluid in the conduits 25 and 26 is supplied from the pump I9 through a fluid conduit 21 which delivers iluid to the coupling I5. A by-pass or bleed fluid conduit 28 connects the coupling I5 with the reservoir i8. It will be understood that the reservoir i8 may comprise the engine oil sump of the vehicle, and the pump I9 may comprise the engine oil pump or a separate auxiliary Dump.

The coupling I5 is shown in detail in Figs. 2 and 3. As shown in these iigures, the coupling I5 includes a valve housing 29 which is xedly secured to the lower shaft Id and journallcd in a stationary support sleeve 29a. The housing 2S has a central axial bore 30 for rotatably receiving the lower end portion of the shaft I2. A torque lug or coupling member 3| is non-rotatably secured to the shaft I2 by a key 32 disposed in a slot Sil in the shaft I2 and a slot 35 in the coupling member 3|. The coupling member 3! is provided with a pair of integral radially oppositely extending arms or ears 3S, 35 which are disposed in normally spaced relation in a pair oi generally conforming slots 3l, 3l provided in the housing 29 and communicating with the bore 38. As can be seen, there is a mechanical linkage between the shafts I2 and I4 in that rotation of the shaft i2 will cause rotation of the coupling member 3| and consequent rotation of the shaft |l through engagement of the ears 36 with the defining walls oi slots 31. It will also be seen that, due to the normally spaced relation between the ears 38 and the dening walls of the slots 3l', a limited lost motion interval is provided between the shaft I2 and the shaft it when the mechanical linkage of the coupling member 3| is utilized for steering.

Means are provided for controlling and directing the fluid pressure supplied to the coupling I5 through the pressure conduit 21 in order to obtain pressure boosted power steering through the boost cylinder 20. Herein such means comprise a pair of pressure control valves 38, 38 for controlling the fluid pressure from the conduit 2l and a pair of bleed control valves 39, 3S for controlling the bleeding of pressure from the coupling I5 back to the reservoir I8 through the bleed conduit 28. The valves 38 and 33 may be identical and each may comprise an enlarged head portion lill, a reduced diameter stem portion 4|, a frusto-conical valve seat portion `152, a reduced diameter stem et and a skirt portion t5. The head portions la of the valves 38 are slidably disposed in respective conforming bores S extending coaxially outwardly from one of the slots 3l, and the head portions 4|) of the valves 39 are slidably disposed in conforming relation in respective conforming bores 4'! extending coaxially outwardly from the other of the slots 3l, The skirt portions 5 of the valves 38 and 39 are slidably disposed in conforming bores 48 formed in respective closure plugs or caps i9 which are threadably inserted into threaded bores 5t formed in the housing 29 ooaxially outwardly of the bores 46 and lil. Respeetive compression springs 5| are disposed in reduced diameter recesses 52 formed in the ends of the skirt portions 45. The springs 5| act between the skirt portions and the plugs 29 to urge the respective valves 38 and 3Q inwardly. The frustoconical seat portions [52, are adapted for seating against valve seats trl provided at the outer ends of the bores 4S and fil. lt will be noted that the valves 38 and 3E are of the pressure balanced type so that there will be no net fluid pressure bias on the valves whether in the opened or closed positions. With the coupling member 3| in the neutral position as shown in Fig. 2 the valves 38 and 32 are held open by means of rounded ends 55 formed on the valve heads 4|? which abut the ears 36.

Communication is aiorded between respective pairs of bores i and lil by means of interconnesting passages 55, 56 when the corresponding pairs of valves are open. Fluid under pressure from the conduit 2l is supplied to the bores l5 through an inlet passage 5l in the stationary support sleeve 29a, an annular groove 57a in the valve housing 29 and respective branch passages 58, 58. Communication between the bleed conduit 28 and the bores 4l is provided through a bleed passage 59 in the stationary support sleeve 29a, an annular groove 59a in the valve housing 29 and respective branch passages 55, 6I).

One side of the boost cylinder piston 23 is referenced through the conduit 25, a port 6| in the stationary sleeve 2da, an annular groove Gia in the valve housing 29 and a passage 5|?) to one of the interconnect passages 56, and the other side of the piston 2S is referenced through the conduit 25, a port 82 in the stationary sleeve 29a, an annular groove 62a in the valve housing 29 and a passage 62h to the other interconnect passage 56.

As will be seen, when the member 3| is in the neutral position as shown in Fig. 2, all of the valves 38 and 39 are held open equally so that the iiuid supplied through the passages 53 passes by the open valves 35, through the interconnect passages 55, past the open valves 39, into the bleed passages 68 and thence back to the reser- Voir i3. Since the pressure drops through the respective valves 38 and 39 are equal, the pressures in the passages 5t are equal and no power boosted movement of the pitman arm Il will occur.

In operation, steering effort applied to the steering wheel Ill is transmitted through the upper steering shaft l2 to the coupling member 3| to cause consequent rotation of the member 3| about the axis of the shaft I2. If the power cassa-342 boost system is inoperative for any reason, torque transmitted to the coupling member 3| will be imparted to the lower shaft i4 through mechanical engagement with the valve 'housing Eil after the member 3| has been rotated through the limited lost motion interval until opposite sides of the lugs or ears 35 abut the respective defining walls of the slots 3l. Thus, the steering mechanism of the present invention is provided with fail safe characteristics and a substantially conventional mechanical steering linkage is provided so that the dirigible wheels of the vehicle may be readily steered when the pump li? is inoperative for any reason.

In operation with the power boost system functioning, rotary motion supplied to the coupling member 3| urges one of the valves andthe diagonally opposite valve 3E toward further open positions against the bias of the springs 5i. At the same time, the other valve springs 5i urge the other pair of diagonally opposite valves it and 39 toward closed positions. As the diagonally opposite pair of valves 3'8 and 3S are respec tively moved toward further opened and closed positions when the coupling member 2i is rotated in the lost motion interval, the pressure drops through the closing valves will be increased and the pressure drops through the further opening valves will be decreased. As a result, the fluid pressure in one of the interconnect passages 55 will be increased while the iiuid pressure in the other interconnectpassage 5t will be decreased. Hence, the pressure on one side of the piston 23 will be increased and the pressure on the other side of the piston E3 will be decreased. This will result in movement of the piston 23 in one direction to give a power boosted movement of the pitman arm Il and will result in steering movement of the dirigible wheels in one direction. If the steering wheel il) is turned in the opposite direction it will be readily seen that the boost cylinder piston 23 will also be urged in the opposite direction to steer the dirig?. e wheels correspondingly.

It should be noted that the power boost force ap-plied by the piston 23 varies as the steering eifort applied to the steering wheel l@ since increased steering effort will result in increased movement of the control valves which provides an increased pressure differential on the piston 23. Also, the speed of movement of the boost cylinder piston 23 will depend upon the rate of rotation of the steering wheel it up to the maximum rate of power boosted rotation which will occur' when the coupling member 3i is rotated so fast that the ears 35 abut the corresponding sides of the slot 3l to impart maximum movement to the valves 33 and 39.

In conclusion, the present invention provides a very much simplified power steering mechanism which can be installed in a conventional mechanical steering linkage with a minimum of medincation. The only modifications necessary in such an installation are the separation of the steering shaft into two parts, the provision cf the simplied coupling between the two parts, and the provision of a pump and a power boost cylinder including the pressure conduits therefor. It is not necessary to revise the conventional mechanical steering linkage arrangement or to modify the steering gear box. Very simple and inexpensiveprovision can be made for alternately installing power steering or mechanical steering in vehicles in the same model by providing for alternate installation of Vthe'simplified coupling of the present invention orv an'ordinary .mechanical coupling init'sipl'ace.

The coupling of this invention is of Van improved balanced valve type which vis actuated through movement o'f the steering shaft itself. A certain amount of feel is built in in the form of spring resistance by the valve springs. The valving arrangement in the coupling is such as to give coordination between movement of the steering wheel and the steering of the Vdirigible wheels both as to rate of movement vand 'as to steering e'ort. v

It will be understood that modifications and variations may be effected without departing from the scope-of the novel concepts of thepresent invention. For example, the power boost mechanism may be utilized for actuating many types of movable elements other than vehicle dirigible wheels.

I claim:

- 1. Mechanism for steering the dirigible wheels of a vehicle comprising a manually rotatable steering shaft, 'a second rotatable steering shaft axially aligned with said manually rotatable shaft, a coupling member secured to one of said shafts and associated with the other shaft to rotate the same in response to rotation of said one shaft, said coupling member providing a limited lost motion interval between the shafts, means including a pitman arm associated with said second shaft for steering the dirigible wheels in response to rotation of the second shaft, a fluid motor having a reciprocable piston connected to said pitman arm for moving the same, a 'fluid source connected to said motor for providing fluid pressure other than atmospheric, fluid pressure control valves associated with said other shaft and having portions abutting said coupling member for actuation thereby in said lost motion interval, said coupling member normally holding said valves open, means on said valves for accomplishing differential opening and closing of said valves by movement of said coupling member, whereby movement of said manually rotatable'shaft in either direction effects differential opening `of some and closing of others of said valves to provide a net differential pressure bias on said fluid actuated piston to effect power steering of the vdirigible wheels, said net differential pressure bias on said fluid actuated piston being controlled by said valves both to and lfrom said piston, said coupling member also providing for manual steering of'saicl dirigible wheels in the event of failure of said power boost means.

2. Mechanism 'for steering the dirigible wheels of a vehicle comprising a manually rotatable steering shaft, a second rotatable steering shaft axially aligned with said manually rotatable shaft, a coupling member secured to one of said shafts and 'associated with the other shaft to rotate the same in response to rotation of said one shaft, said coupling member providing a limitedlost motion interval between the shafts, means including a pitman arm associated with said second shaft for steering the dirigible wheels in response to rotation of the second shaft, a fluid motor having a reciprocable piston connected `to said .pitman arm for moving the same, a source of fluid, four fluid control valves associated with said other shaft and having portions abutting said control member, said coupling member normally holding said valves open, iluid' conduit means passing said fluidrthrough said valves when opened both tosaid fluid motor and backtovsaidffluid source, said valves lhavingsur-I.

face means thereon cooperating with said fluid conduit means to provide variable area openings between fully opened and fully closed position, whereby movement of said manually rotatable shafts in one direction in said lost motion interval causes movement of two of said valves toward closed position to provide an increased fluid pressure dependent upon the differential area opening provided by said valve means on one side of said piston to steer said dirigible Wheel in one direction by control of the differential pressure to and from said reciprocable piston and whereby movement of said manually rotatable shaft in the other direction in said lost motion interval causes movement of said other two valves toward closed position to provide an increased fluid pressure dependent upon the differential area opening provided by said valve means on the other side of said piston to steer said dirigible wheels in the other direction by control of the differential pressure to and from said reciprocable piston, said coupling member providing for manual steering of said dirigible wheels in the event of failure of said power boost means.

3. In mechanism for steering the dirigible wheels of a vehicle and including a manually rotatable steering shaft, means associated with the shaft for steering the dirigible wheels in response to rotation of the shaft, said means comprising a coupling member permitting a limited lost motion interval of the shaft and completing a mechanical steering connection between the shaft and the dirigible wheels beyond said lost motion interval, a uid motor having a reciprocable piston connected to said means for steering the dirigible Wheels in response to movement of the piston, two pressure control valves, two bleed control valves, said coupling member normally holding said valves open, a source for supplying fluid under pressure other than atmospheric, conduit means referencing fluid from said source to said pressure control valves and through the same when open to the opposite sides of said iluid motor piston, conduit means referencing the fluid downstream of said pressure control valves through said bleed control valves when open to atmospheric pressure, means on each of said valves which cooperates with said conduit means to provide variable differential area openings between fully opened and fully closed positions of said valves, whereby movement of said shaft in one direction in said lost motion interval acts through said coupling member to cause move-- ment of one of said pressure control valves and one of said bleed control valves toward closed position to cause a net differential pressure bias on said piston to steer the dirigible wheels in one direction and whereby movement of said shaft in the other direction in said lost motion interval acts through said coupling member to cause movement of the other of said pressure control valves and the other of said bleed control valves toward closed position to cause a reverse net differential pressure bias on said piston to steer said dirigible wheels in the other direction, said net differential pressure bias being accomplished by said valves which control the flow of dinerential pressure to and from the opposite sides of said piston.

4. In mechanism for steering the dirigible Wheels of a vehicle and including a manually rotatable steering shaft, means associated with the shaft for steering the dirigible wheels in response to rotation of the shaft, said means comprising a coupling member secured to said shaft and having a pair of radially outwardly extending ears, an element having slots therein receiving said ears in normally spaced relation to provide a limited lost motion interval between the coupling mem er and the element, said coupling member and said element completing a mechanical steering connection between said shafts and said dirigible Wheel beyond said lost motion interval, a fluid motor having a reciprocable piston connected to said means for steering the dirigible wheel in response to movement of the piston, two pressure control valves including springs biasing the valves toward closed position, said pressure control valves having tapered metering surfaces thereon, two bleed control valves including springs biasing the valves toward closed position, said bleed control valves having tapered metering surfaces thereon, said coupling member normally holding said valves open, a source of fluid under pressure, conduit means referencing iiuid from said source to said pressure control valves and through the same when opened to the opposite sides of said fluid motor piston, conduit means referencing the fluid downstream of said pressure control valves through said bleed control valves when opened to atmospheric pressure, whereby movement of said shaft in one direction in said lost motion interval acts through said coupling member to move one of said pressure control valves and one of said bleed control valves toward further open positions to thus proportionately increase the flow area therethrough and said springs act to move the other valves toward closed positions to thus proportionately decrease the flow area therethrough to increase the pressure on one side of the piston to steer said dirigible wheels in one direction, and Whereby movement of said shaft in the other direction in said lost motion interval acts through said coupling member to move the other of said pressure control valves and the other of said bleed control valves toward further open positions to thus proportionately increase the flow area therethrough and said springs act to move the remaining valves toward closed positions to thus proportionately decrease the flow area therethrough to increase the pressure on the other side of said piston to steer said dirigible wheels in the other direction, said proportional increase or decrease of flow area through said valves being accomplished by said tapered metering surfaces.

5. In mechanism for steering the dirigible wheels of a vehicle and including a manually rotatable steering shaft, and a second rotatable shaft axially aligned with said manually rotatable shaft, means associated with the shafts for steering the dirigible wheels in response to rotation of the manually rotatable shaft, said means comprising mechanism associated with said second shaft for steering the dirigible wheels in response to rotation of the second shaft, a coupling member secured to said manually rotatable shaft and having a pair of radially oppositely extending ears, an element secured to said second shaft and having slots therein receiving said ears in normally spaced relation to provide a limited lost motion interval between the coupling member and the element, said coupling member and said element completing a mechanical steering connection between said shafts beyond said lost motion interval, a fluid motor having a reciprocable piston connected to said last-mentioned mechanism for steering the dirigible Wheels in response to movement of the piston, two pressure control valves having tapered metering surfaces thereon and including springs biasing the valves toward closed positions, two bleed control valves having tapered metering surfaces thereon and including springs biasing the valves toward closed positions, said pressure control valves having portions abutting one of said control member ears and said bleed control valves having portions abutting the other of said control member ears whereby said coupling member ears normally hold said valves open, said pressure and bleed control valves having surfaces thereon in addition to said tapered metering surfaces, all of which cooperate to balance the valves against fluid pressure bias in any position, a source of fluid, a pump adapted to draw fluid from said source and to pressurize the fluid, conduit means referencing fluid from said pump to said pressure control valves and through the same when open to the opposite sides of said fluid motor piston, conduit means referencing the fluid downstream of said pressure control valves through said bleed control valves when opened back to said source, whereby movement of said manually rotatable shaft in one direction in said lost motion interval acts through said coupling member ears to move one of said pressure control valves and one of said bleed control valves further open with said springs moving said other valves toward closed positions to thus increase and decrease respectively the differential area openings of said valves to provide an increased differential fluid pressure on one side of said piston to steer said dirigible wheels in one direction and whereby movement of said manually rotatable shaft in the other direction in said lost motion interval acts through said coupling member ears to move the other of said pressure control valves and the other of said bleed control valves further open with said springs moving the remaining valves toward closed positions to thus increase and decrease respectively the differential area openings of said valves to provide an increase differential fluid pressure on the other side of said piston to steer said dirigible wheels in the other direction, said increase or decrease of differential area opening being accomplished by said tapered metering surfaces on said valves.

6. Valving mechanism for controlling fluid pressure comprising a valve housing having a fluid inlet port, a iiuid outlet port and two controlled fluid pressure ports, a pair of pressure control valves having taperedv` metering surfaces thereon and arranged in parallel in said housing for controlling fluid flow into said housing through said inlet port and including valve springs biasing the valves toward closed position, a pair of bleed control valves having tapered metering surfaces thereon and arranged in parallel in said housing for controlling fluid ilow out of said housing through said outlet port and including valve springs biasing the valves toward closed position, said pressure and bleed control valves having pressure balance surfaces thereon in addition to said tapered metering surfaces, all of which cooperate to balance the valves against fluid pressure bias when in any position, said housing having a pair of fluid interconnect passages connected to the respective controlled pressure ports and interconnecting respective pairs of pressure control and bleed control valves, and a control member associated with said valves and having a neutral position in which the pressure control valves and the bleed control valves are held open respectively equally, said control member being arranged so that movement thereof in one direction moves one pressure control valve and the unconnected bleed control valve toward further open positions while allowing said springs to move the other valves toward closed positions thereby proportionately increasing and decreasing respectively the flow area through said valves and so that movement of the control means in the other direction reverses the movements of the valves, whereby the uid pressures at the controlled pressure ports vary in .accordance with the difference between the effective open areas through the pressure control valves, said difference in said effective open areas being accomplished by the relative position of said metering surfaces through movement of said valve.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,144,552 Lardner et al June 29, 1915 1,719,875 Cooper July 9, 1929 1,907,211 Moffet May 2, 1933 1,910,600 Fitch May 23, 1933 2,028,451 Hodge et al Jan. 21, 1936 2,293,555 Mercier Aug. 18, 1942 2,554,843 Staude May 29, 1951 

